EIS-4 is a simple to install GSM phone unit that calls you when visitors visit your home or office, allowing you to control visitor access through your mobile device and/or landline phone. This unit is easily accessible allowing up to 1000 caller ID numbers as well as backlighting for easy visibility. To install, post or surface mount the ESI-4 then connect to a power supply, create a phone number for the unit to dial, and insert a SIM card. Features: